Large quantities of environmentally persistent compounds have been disposed of on land, air and water and which accumulate on land and in water. The term "environmentally persistent" includes those compounds which are only slowly degraded or not degraded at all in the natural environment. Many remain as potentially dangerous and toxic materials to plant and animal life. Others appear innocuous but the effects may be long term, e.g. causing mutations or lowering immunity to disease. Yet others promote the growth of unwanted species. Obvious blots on the landscape may be caused by deliberate or accidental release of large quantities of such compounds, e.g. as a result of rupture of containers or pipelines. More subtle is the deliberate use of chemicals which make their way to waterways, e.g. the use of pesticides on farmland, mine tailings ponds which seep into water courses.
There is growing concern over the contamination of land and water bodies, especially as it relates to the food chain and to the purity of drinking water. Various chemical methods have been used to convert toxic materials into relatively harmless materials. However, in cleaning up large contaminated bodies such methods tend to be extremely costly. It would be preferable to be able to use natural products in order to clean up contaminated bodies.
It is known to use natural materials such as sphagnum moss for absorbing materials such as oils from contaminated substrates such as soil. Absorption of the oils seems to be dependent upon the high surface area of the sphagnum moss. It is unsuitable, however for removing trace quantities of contaminants. Starch xanthates have also been used for removal of metals but carbon disulphide is released during the removal process. Cooked cereals, e.g. puffed rice, have been used to cause agglomeration of oil from the surface of water, as indicated by Arsenault et al in U.S. Pat. No. 4,969,774 which issued Nov. 13, 1990. Such a method is dependent on the oil floating on the water's surface. A method has been found which is particularly efficacious for removing very low concentrations of organic chemicals and heavy metals, which are dissolved or otherwise entrained in aqueous or gaseous fluids and is relatively inexpensive. Surprisingly it has been found that this absorption can be accommodated using commonly available materials which are derived from natural products.